Appeal to motive
The problem with this sort of fallacy is that addressing one's motives, instead of the argument put forth, is a type of red herring. Additionally, unless the person appealing to motive is telepathic, how could the person know one's secret motives, and whether they are part of the decision making process?
- "You atheists are rejecting my evidence because you want to sin."
- "Those scientists are only promoting global warming because they want more funding."
- "You don't want to have a professional apologist on your show because you're scared of the truth."